Onions Allium cepa
The onion (or allium) family is a large and diverse one containing over 500 species. With such a large range of species the origins of the modern (or globe) onion are a bit blurred. It has not one but five possible wild plants it could have evolved from, all of which grow in the central Asian region.
It is thought that bulbs from the onion family have been utilised as a food source for millennia. In Palestinian Bronze Age settlements traces of onion remains were found along side fig and date stones dating back to 5000 BC! It would be pure conjecture to suggest these were cultivated onions. The archaeological and literary evidence suggests cultivation probably took place around two thousand years later in ancient Egypt. This happened alongside the cultivation of leeks and garlic and it is thought that the slaves who built the pyramids were fed radishes and onions.
"…It is thought that the slaves who built the pyramids were fed radishes and onions."
It may come as no surprise that it was the Romans who introduced the onion family to Europe. The origins of its name are also Roman or at least Latin. The Late Latin name unio was used to describe a species of onion resembling a single white pearl. This was later formed the basis for the French, ‘Oignon’ and then later the English, ‘Onion’.
Why Does the Onion Family Smell? All closely related plants to the onion, (Leeks, Shallots, Garlic, Chives etc) contain thioallyl compounds or alliins. When cut or crushed the alliin (an amino acid), within the garlic or onion is converted by an enzymatic reaction into allicin, this quickly breaks down into sulphide compounds. Sulphide compounds are aromatic and this is what gives all the plants in the onion family their distinctive smell. So to put it simply -
• The onion family stinks because of a chemical change from alliin to sulphide compounds and sulphur stinks.
Onion Family Health and Nutrition
Garlic contains by far the highest concentration of alliins and it has been used medicinally for centuries and was used as an antiseptic since classical times. The Romans often used garlic and would drink a solution of around 5-10 bulbs boiled down in a small bucket of wine for a hangover cure.
It has also been found that alliins can prevent the growth of malignant cells. In other words they are an anti-carcinogen and can help prevent the growth of cancerous cells in animals. It has been documented that in areas of high garlic and onion consumption rates of stomach cancer are relatively low.
There is mounting evidence that all members of the onion family have a positive effect in lowering incidences of heart disease. Trials in the mid-nineties showed a drop in cholesterol levels of a test group when given garlic powder.
It would appear that onions play a much more important anti-carcinogen or cardioprotective role than a nutritional one (see below). However they do add a distinctive flavour, smell and texture to many meals and form the initial stage in many recipes.
- (All average size),Onion Raw,Onion Fried in Oil,Pickled Onion
- Energy(Kcal) 54 66 4
- Protein (g) 1.8 0.9 0.1
- Carbohydrate (g) 11.9 5.9 0.7
- Sodium (mg) 5 2 68
- Calcium(mg) 38 19 3
I planted some onion sets in August to grow over winter; they should be ready by late spring/early summer. These are the first onions I have grown, as I have always been able buy them cheaply in bulk from a nearby Indian grocery shop. This year however there are only three of us in our house and I found the large bags to be a false economy. They would more often than not sprout or go off before I had a chance to eat them all.
In addition to my August sown onion sets I shall raise some from seed in January indoors to plant out in April and some from seed outdoors in March. They can also be planted out in sets in spring, which will be ready by late August/ early September.
The ground should be well prepared for growing onions. Clay soils should be worked into a fine tilth working in plenty of organic matter. It may be an idea to prepare the ground before using a green manure such as clover or phacelia. I have sown a patch of phacelia for this very reason, ideally this should be planted between March and September but if you put some down in early October it should grow a little before winter properly sets in.
Most seed packets will give you an idea of the depth of sowing and spacing. I always try and imagine what the plant will look like when mature and give it a little more room than that. So each onion will be planted about 2 ½ onion sizes from its neighbour. This seems to work with most crops but they can choke each other if too tightly spaced, as the roots need a certain amount of room to grow into.
So to recap
• Prepare the soil first either with a green manure or by working in some organic matter.
• If planting in spring it may be an idea to expose the ground to some frosts to break it up.
• Plant indoors or under glass in January to plant out in April
• Or plant in cloches in February (same with garlic) or from seed in March.
• Harvest August – September.
• Or plant in sets in August for harvest in late spring/early summer.
One final point, onions should not be grown on the same patch year after year. This goes for leeks, garlic and shallots too, they all should be sown as part of a crop rotation scheme.